1. Field of the Invention
The present invention relates to a polyamide of a novel structure and an electrophotographic photosensitive member which has an interlayer containing the polyamide.
The present invention also relates to an electrophotographic apparatus, a device unit, and a facsimile machine employing the electrophotographic photosensitive member.
2. Related Background Art
In repeated use of a Carlson type electrophotographic photosensitive member, one of the important characteristics of the member for stably obtaining high-quality images is the stability of the dark area potential and the light area potential. Therefore, improvement of carrier injection efficiency, improvement of adhesiveness of the photosensitive layer to the support, improvement of coating properties of the photosensitive layer, and provision of an interlayer between a support and a photosensitive layer to cover defects on the support have been proposed.
Known materials useful for the interlayer include polyamides (JP-A-Sho-46-47344 (The term "JP-A" as used herein means a Japanese Patent Laid-Open Application), JP-A-Sho-52-25638, and JP-A-Sho-58-95351), polyesters (JP-A-Sho-52-20836 and JP-A-54-26738), polyurethans (JP-A-Sho-49-10044 and JP-A-Sho-53-89435), casein (JP-A-Sho-55-103556), polypeptides (JP-A-Sho-53-48523), polyvinyl alcohol (JP-A-Sho-52-100240), polyvinylpyrrolidone (JP-A Sho-48-30936), vinyl acetate-ethylene copolymers (JP-A-Sho-48-26141), maleic anhydride ester copolymers (JP-A-Sho-52-10138), polyvinylbutyral (JP-A-Sho-57-90639 and JP-A-Sho-58-106549), quaternary ammonium-containing polymers (JP-A-Sho-51-126149 and JP-A-Sho-56-60448) and ethylcellulose (JP-A-Sho-55-143564), and so forth.
The interlayer comprising the above-mentioned material, however, has the resistance susceptible to temperature and humidity, so that the stability of potential characteristics and high quality of images cannot always be achieved over environmental conditions of from low temperature and low-humidity to high temperature and high humidity.
For example, at low temperature and low humidity, the resistance of the interlayer tends to become high, which may cause rise of a light-area potential or a residual potential on repeated use of the photosensitive member, thereby causing instability of image quality such as occurrence of fogging (in positive development), and fall of image density (in reversal development).
On the other hand, at high temperature and high humidity, the resistance of the interlayer tends to become low, which may cause lowering of the barrier function to increase the carrier injection from the support side and to lower the dark area potential, thereby causing black spot-like defects or fogging of the image.